In this article, we investigate the optical and electrical properties of surface plasmon polariton of Ag nanoparticles influenced by surrounding medium with different conductivities. Ultraviolet-visible infrared spectra and surface enhanced Raman scattering show that when the Al2O3 films are used as a surrounding medium, the optical loss caused by surface plasmon polariton of Ag nanoparticles will be reduced and the surface electromagnetic (EM) field will be enhanced, while conductive substrate may lead to the surface plasmons transmitting along the substrate layer then reduce the EM field and enhance the optical absorption. This property provides an effective approach to the use of optical and electrical properties of surface plasmon polariton in thin film solar cells when a thin film of Al2O3 is added as a cover layer.